Despite the technological "comforts" of the ISS, a year in space - the longest space mission in American history - has been described as the epitome of extreme, with extraordinarily high physical stakes. Following Scott in space and his identical twin Mark Kelly at home on Earth, the specials will tell the story of what it takes, mentally and physically, to spend a year in space and then, using what NASA has learned from the Kelly brothers, what it means for humanity as we journey to Mars and beyond.